1. Technical Field
The present invention relates to an aluminum alloy electric wire for use in an automotive wire harness and the like, and to an automotive wire harness using the same.
2. Related Art
An aluminum alloy electric wire including an aluminum alloy strand is known as an electric wire for use in an automotive wire harness and the like.
In recent years, it has been desired to reduce a diameter of an aluminum alloy electric wire in order to reduce weight of an automobile. An electric wire with a smallest diameter in JASO D 603, which is a standard for the present automotive aluminum alloy electric wires, is an electric wire in which a cross-sectional area of an aluminum alloy stranded wire conductor as a bundle of a plurality of the aluminum alloy strands is 0.75 sq (mm2). Moreover, in this standard, as performance required for the aluminum alloy strand that composes the aluminum alloy stranded wire conductor with a cross-sectional area of 0.75 sq, there are prescribed tensile strength of 70 MPa or more, elongation at break of 10% or more, and conductivity of 58% IACS or more.
As a conventional technology regarding the aluminum alloy strand, Japanese Unexamined Patent Publication No. 2010-77535 describes an aluminum alloy wire that contains predetermined amounts of Mg, Si and Cu, in which conductivity is 58% IACS or more, and elongation is 10% or more. Moreover, an embodiment of Japanese Unexamined Patent Publication No. 2010-77535 describes an aluminum alloy wire with tensile strength of 124 to 134 MPa.
Moreover, Japanese Patent No. 5128109 describes an aluminum electric wire conductor, which is composed by twisting a plurality of aluminum alloy strands, and contains predetermined amounts of Mg and Si, in which tensile strength is 240 MPa or more, elongation at break is 10% or more, and conductivity is 40% IACS or more.
Furthermore, Japanese Unexamined Patent Publication No. 2013-44038 describes an aluminum alloy wire that contains Fe, Mg and Si, in which tensile strength is less than 240 MPa, and elongation at break is 10% or more.
Incidentally, since the weight of the automobile is needed to be reduced, it has been desired to further reduce the diameter of the aluminum alloy electric wire. Aluminum alloy electric wires, which are expected to appear in the future with reference to a size of the automotive copper electric wire prescribed in JASO D 611, are those in which cross-sectional areas of the aluminum alloy stranded wire conductor are 0.5 sq, 0.35 sq, 0.22 sq, 0.13 sq and the like.
However, if the cross-sectional area of the aluminum alloy stranded wire conductor is reduced, then a load capacity of the aluminum alloy electric wire is decreased. Therefore, in order that the aluminum alloy electric wire can have a sufficient load capacity, it is necessary to increased strength of the aluminum alloy strand. For example, in order that an aluminum alloy electric wire, in which such a cross-sectional area of the aluminum alloy stranded wire conductor is 0.5 sq or less, can obtain a load capacity equivalent to that of an aluminum alloy electric wire, in which a cross-sectional area of the aluminum alloy stranded wire conductor is 0.75 sq, it seems necessary that the tensile strength of the aluminum alloy strand be 165 MPa or more.
Moreover, in order that the aluminum alloy electric wires can be used in an automotive application such as an automotive wire harness, it is necessary that the aluminum alloy strand have appropriate elongation at break and conductivity in addition to high strength.
On the other hand, the aluminum alloy strand in Japanese Unexamined Patent Publication No. 2010-77535 has low strength. Accordingly, when such an aluminum alloy electric wire, in which a cross-sectional area of the aluminum alloy stranded wire conductor is smaller than 0.75 sq, is produced, the strength of the aluminum alloy electric wire is expected to be insufficient.
Moreover, in the aluminum alloy strand in Japanese Patent No. 5128109, when a wire diameter is set to φ0.32 mm, then the number of crystal grains observed on a cross section of the strand is decreased, and the elongation at break is decreased. Therefore, if the aluminum alloy electric wire, in which the cross-sectional area of the aluminum alloy stranded wire conductor is smaller than 0.75 sq, is produced from this strand, then it is apprehended that such ductility of the aluminum alloy electric wire may be insufficient.
Furthermore, Fe is added to the aluminum alloy strand of Japanese Unexamined Patent Publication No. 2013-44038. Therefore, if the aluminum alloy electric wire, in which the cross-sectional area of the aluminum alloy stranded wire conductor is smaller than 0.75 sq, is produced from this strand, then it is apprehended that the conductivity of the aluminum alloy electric wire may be decreased.